Large industrial and motive power lead acid storage batteries typically are manufactured in small lots in a job shop type environment. Various of the manufacturing steps, including the attachment of terminal post straps onto the lugs of battery cell plate groups, are inherently slow, labor intensive, and not easily subject to change-over for different sized batteries.
A common method of attaching terminal post straps onto plate lugs has involved securing a plate group in a comb-like fixture in a burning box, locating a pre-cast terminal post and strap on the plate group, melting the plate lugs and the terminal post strap by means of a manually held gas torch, adding additional lead by melting a lead stick, and simultaneously stirring and mixing the melted lead to break down surface tension between the lead alloys and to free the mixture of entrained impurities. Not only does such manual torch burning fail to lend itself to use in automated battery production lines, the procedure cannot be carried out with consistent quality and can create a hazard to the environment of the worker.
Another method of attaching straps to plate lugs has entailed compressing and positioning the plate group in a basket-like container, inverting the plate group and positioning the lugs thereof in a mold, adding molten lead to cast straps on the lugs, removing the plate group with the cast on straps from the basket, and re-compressing and positioning the plate group into a battery container.
In sealed, valve-regulated lead acid batteries, the plate group includes separators made of relatively fragile glass mat material between the individual plates. Repeated compression and handling of the plate group can damage the separators and adversely effect battery performance and life. Even in unsealed, flooded lead acid storage batteries which do not utilize such glass mat separators, the plates are fragile and a plastic top separator piece must be used to prevent damage to the separators from insertion of a hydrometer for testing the acid during battery usage.
While proposals have been made for the automated casting of straps onto battery plate lugs, these proposals have not lent themselves to the small lot production of different size batteries. Relatively expensive, precision molds are required for the casting operation, and a different mold is required for each different plate group size to be manufactured. The lengthy change-over time also makes conventional automated cast-on-strap methods impractical in small lot battery production.